leonard



March 10, 1964 L. H. LEONARD, JR 4 REFRIGERATION APPARATUS 0 O '0 O 0 0O (cw .1 I I 27 INVENTOR.

l LOUIS H. LEONARD JR.

ATTORNEY.

March 10, 1964 LEONARD, JR 3,123,984

REFRIGERATION APPARATUS Filed Dec. 27, 1960 2 Sheets-Sheet 2 INVENTOR.

LOUIS H. LEONARD JR.

ATTORNEY.

rates Patent 3,123,984 Patented Mar. 10, 1964 fine 3,123,984REFREGERATKON APPARATUS Louis H. Leonard, in, De Witt, N.Y., assignor toCarrier Corporation, Syr cuse, N.Y., a corporation of Delaware FittedDec. 27, 1am, Sci. No. 83,129 9 Claims. (Cl. 62-125) This inventionrelates to refrigeration machines and more particularly to a specializedconstruction adapted for use with absorption refrigeration machineswhereby leaks in liquid cooled heat exchangers may be detected.Constructions of the type herein described find a particular applicationaboard naval or other seagoing vessels and especially on submarineswhich are particularly susceptible to the occurrence of leaks due to thehigh submergence pressures encountered and wherein the detection ofleaks is considered of substantial importance.

Absorption refrigeration machines conventionally comprise an absorber,an evaporator, a generator and a condenser operatively connected to forma refrigeration system. A more complete description of the type ofsystem herein referred to is contained in Leonard application, SerialNo. 2,206, filed January 13, 1960; now Patent No. 3,054,272. In suchsystems, both the condenser section and the absorber section generallycomprise water-cooled heat exchangers. In the absorber section, it isnecessary to remove the heat of condensation and dilution liberated byvaporized refrigerant as it is absorbed in the absorbent solution. Inthe condenser, it is necessary to remove the heat liberated bycondensation of refrigerant vapor, or stated in another way, it isnecessary to cool the refrigerant vapor sufficiently to cause it tocondense. In each of these instances, it is common practice to provide aheat exchanger of the tube-and-shell type.

A tube-and-shell type heat exchanger basically comprises a pluraiity ofheat exchange tubes passed through and secured in a leak-tight manner toa tube sheet which forms an end wall of a heat exchanger shell. A fluidheader is secured to the end of the tube sheet and forms a fluidreceiver or distributor for the passage of a cooling fluid such as waterwhich passes through the heat ex change tubes. A similar construction isgenerally formed at the other end of the heat exchanger shell and meansis provided to pass the cooling fluid to one header from which it passesthrough the heat exchange tubes to provide the desired cooling of a gasor liquid in the interior of the shell. The cooling fluid, which haspicked up heat in its passage through the heat exchange tubes, is thenemptied into the header at the opposite end of the heat exchanger fromwhich it is suitably discharged.

In conventional absorption refrigeration machines, the pressure exertedby the cooling fluid at the joints between the heat exchange tubes andthe tube sheet need not be extremely high nor are undue mechanicalstresses likely to occur. Consequently, conventional rolling techniquesfor making a leak-tight joint between the heat exchange tubes and thetube sheets may be entirely adequate to prevent leakage. But, when anabsorption refrigeration machine employing a tube-and-shell heatexchanger is installed in a submarine, it is highly desirable from thestandpoint of economy and simplicity of operation to utilize sea wateras the cooling medium flowing through the heat exchange tubes.Consequently, the pressure exerted on the joints between the heatexchange tubes and the tube sheet may be equal to or greater than thesubmcrgence pressure of the sea Water at the depth at which thesubmarine is operating. This pressure may, therefore, be of the order ofseveral hunderd pounds per square inch when a submarine is operating ata substantial depth.

Under these conditions, the stresses imposed on the joints between theheat exchange tubes and the tube sheet may be extremely severe andsuflicient to cause small leaks to develop in the joints. While smallleaks may not seriously impair functioning of the refrigeration machinewhen used under normal surface operating conditions, they may be ofsufficient magnitude to seriously reduce the refrigeration capacity ofthe absorption system when subjected to the great pressures encounteredduring submergence of the vessel. Furthermore, such leaks tend to becomeprogressively worse and in time, the capacity of the machine may begreatly impaired under circumstances where it is difficult or impossibleto correct the situation, as when fully submerged. In addition, leakageof sea water into the interior of an absorption refrigeration machine isextremely deleterious, not only because it seriously impairs thefunctioning of the absorbent solution, but also it may flood the machineor cause corrosion in its interior. Because of the very high heat loads,a submarine may be virtually disabled by failure of its air conditioningwhile operating below the surface of the ocean. Consequently, it isimportant to ascertain the existence of such leaks before they becomeserious so that proper corrective measures may be taken when the vesselis in port.

Since the interior of tube-and-shell heat exchangers such as used inabsorption refrigeration systems is closed and not exposed to view, andsince the existence of small leaks is generally not apparent until theyhave become of sufficient size to impair the functioning of therefrigeration system, it would be highly desirable to provide some meansof detecting these small leaks immediately upon their occurrence. Asimilar problem exists to a somewhat lesser degree in surface operatingvessels at times when they are subjected to unusually severe mechanicalstresses and strains. Therefore, it is also desirable to quickly locatethe existence of leaks which may become progressively worse under severeoperating conditions in such vessels.

Accordingly, it is the principal object of the invention to provide arefrigeration machine having improved means for detecting the existenceof a leak in its heat exchangers.

It is a further object of this invention to provide an improved methodand means for detecting leaks in a heat exchanger.

It is a still further object of this invention to provide an improvedsubmarine refrigeration system.

In a preferred embodiment of this invention, these and other objects areachieved by providing a pair of tube sheets at the ends of the heatexchangers in the condenser and absorber sections of an absorptionrefrigeration machine. The pair of tube sheets are spaced from eachother to form a chamber which is filled with a relatively incompressiblefluid such as octyl alcohol (Z-ethyl-n-hexanol) which is noncorrosiveand which is compatible with the fluids within the refrigerationmachine. Means are provided to observe the effects of abnormal pressureson the fluid in the chamber which are indicative of leakage so thatleakage from the chamber into the interior of the heat exchanger orleakage from the exterior of the heat exchanger into the chamber can bereadily detected.

Such a construction possesses the advantage of forming a liquid seal inthe chamber between the tube sheets and the heat exchange tubes as wellas alfording a ready means of ascertaining the existence and type ofleaks at the tube sheets. In the event that fluid within the chamberleaks into the interior of the heat exchanger, no immediate harm needresult because the material chosen can be a liquid, such as octylalcohol, Which is desirably present in the heat exchangers of theabsorption machine under normal operating conditions.

These and other objects of this invention will become apparent byreference to the following detailed description and attached drawingswherein:

FIGURE 1 is a diagrammatic view of an absorption refrigeration machine;and

FIGURE 2 is a fragmentary cross-sectional view of the ends of a heatexchanger each embodying a form of the instant invention.

Referring to FIGURE 1 of the drawing, there is illustrated an absorptionrefrigeration system constructed in accordance with a preferredembodiment of this invention. The absorption refrigeration systemcomprises an absorber section and an evaporator section 11 locatedwithin shell 12. A plurality of heat exchange tubes 13 adapted to passcooling water are located within the absorber section. A spray system 14comprising a plurality of headers and suitable spray nozzles is locatedabove tubes 13 for the purpose of discharging a finely divided spray ofabsorbent solution thereover.

As used herein the term strong solution refers to a solution strong inabsorbing power and the term weak solution refers to a solution weak inabsorbing power.

The term intermediate concentration is used to designate a solutionhaving a concentration intermediate the concentration of weak and strongsolution.

A suitable refrigerant for a system of the type herein describedcomprises vvater and a suitable absorbent solution comprises a solutionof lithium bromide and water. The concentration of lithium bromideleaving the generator may desirably be about 65%.

Adjacent the lower portion of shell 12 and absorber section 10 is a sump15 which is divided by vertically extending partition means 18 into anintermediate strength absorbent solution sump 16 and a weak absorbentsolu tion sump 17. Both sumps collect absorbent solution sprayed overtubes 13 land sump 16 in addition receives strong solution fromgenerator 34- which mixes therein to form absorbent solution ofintermediate strength. A bypass line 1% may be provided to equalizefluid levels in the two sumps if desired. While for purposes ofillustration, partition 18 has been shown as extending longitudinally ofthe machine, it will be appreciated that the illustration is schematicin nature and that partition 18 may extend transversely across sump 15if desired.

Evaporator section 11, which is also located within shell 12, comprisesa pan or vessel 20 within which are disposed a plurality of heatexchange tubes 21 which are adapted to carry a chilled fluid such aswater to suitable heat exchangers located remotely from therefrigeration machine to provide cooling or dehumidification in thedesired areas. Disposed above tubes 21 in the evaporator section is asuitable refrigerant distributor 22 which may include a plurality ofheaders each having a number of sprays in communication therewith toevenly distribute refrigerant over heat exchange tubes 21.

Pan 26, as illustrated in the drawing, has relatively high verticallyextending walls to prevent transfer of re frigerant in the liquid statedirectly to the absorber section even when disposed at substantialangles to their normal position. The vertically extending walls of pan2% terminate in eliminators 23 which provide a tortuous path for thepassage of refrigerant vapor on its way to the absorber and therebyremove droplets of liquid refrigerant from spray system 22 which mayhave become entrained in the refrigerant vapor. Pump 25 passesaccumulated absorbent solution of intermediate concentration from sump16 through lines 26 and 27 to spray system 14 to maintain a continuousspray of absorbent solution over tubes 13.

Pump 28 passes absorbent solution relatively weak in absorptivecapability through lines 29 and 3t to solution heat exchanger 31. Line32 passes the weak solution from solution heat exchanger 31 torefrigerant distribution means 33 of generator 34. Distribution means 33may suitably comprise a header having a plurality of spray nozzles incommunication therewith disposed above the tube bundle 35.

Generator 34 comprises a shell 43 having vertically extending partitionmeans 44-. Partition 44 may be secured to the upper portion of shell 43and divides the generator into a first compartment and a secondcompartment 46. Heat exchange tube bundle 35 is disposed within firstcompartment 45'. Steam inlet 36 and a steam and condensate outlet 37 isprovided to pass steam through the heat exchange tubes within tubebundle 35. A sump 38 having angular side walls is disposed adjacent thelower portion of shell 4-3 adjacent at least one end thereof and servesto receive strong solution concentrated by the generator and pass itthrough line 39 to heat exchanger 31. Preferably, sump 33 comprises apair of sumps at each end of shell 43 each connecting with line 39 andextending below the bottom of shell .3 as Shown in the drawings.

Warm strong solution is passed from generator 43 through line 39 tosolution heat exchanger 31 and is cooled by heat exchange with cold weaksolution passing through the heat exchanger from line 3%? to line 32 onits Way to the generator. The cooled strong solution is then passed fromheat exchanger 31 through line 40 into intermediate absorbentconcentration solution sump 16 of absorber 19. Upon being dischargedinto sump 16 the strong solution is further cooled by flashing due tothe lower pressure in absorber 10 than exists in generator 34. Sump 33and lines 39 and 44 are sized so as to substantially preventaccumulation of solution in generator 34 while permitting gravity returnof the strong solution into sump 16.

First compartment 4-5 and second compartment 46 of generator 34 are incommunication lWith each other adjacent their respective lower portionsbecause partition means 44 extends only part way down from the top ofshell 43.

If desired, tan eliminator 49 may be disposed in second compartment 46to further assure complete elimination of any remaining entrainedsolution. An outlet 50 and a refrigerant vapor line 51 is located aboveeliminator 49 and leaks from second compartment 46 to a condenser 52.

Condenser 52 comprises shell 53 and a sump 55 to collect condensedrefrigerant vapor. A plurality of heat exchange tubes 54 are disposedwithin shell 53. Inlet line 58 and outlet line 59 are provided to passcooling Water, which in the case of a seagoing vessel may comprise seawater, through tubes 54 to extract heat from the vaporized refrigerantand to condense it. Bypass valve 60 may be provided to bypass coolingfluid around tube 54, if desired.

From sump 55 condensed refrigerant flows through line 64 and line 65 andis discharged into evaporator pan 20. Lines 66 and 67 connect toevaporator pan 20 adjacent the bottom thereof for the purpose ofassuring a drainage of the pan irrespective of the angular position ofthe absorption machine. It will be observed that a pair of each of lines66 and 67 should be provided at both ends of pan 20 in order to takecare of both pitch and roll conditions of the vessel. Lines 66 55a 67drain substantially all of the refrigerant from pan 2t preventingrefrigerant accumulation therein. Lines 66 and 67 discharge intorefrigerant storage tank 68 thereby assuring that refrigerant will notbe emptied from pan as into absorber it) under severe conditions ofpitch and roll.

Pump 69 forwards refrigerant from storage tank 68 back through line '74to refrigerant distributor 22 for respraying over heat exchange tubes 21resulting in vaporization of refrigerant due to heat absorbed in theevaporator section from tlhe heat exchange fluid flowing through tubes21 and cooling of the liquid refrigerant in the evaporator due to thelow pressure in the absorber. It will be understood that absorber lit isin open communication with evaporator 11 through eliminators 23 andthrough spaces provided between the bottom of pan 2%) and the sides ofshell 12 at various suitable locations.

vaporization or evaporation of refrigerant in evaporator 11 results incooling of the heat exchange fluid in heat exchange tube 21 due to theheat which is removed from the heat exchange fluid to convert therefrigerant from a liquid state to a vapor state. Consequently, thefluid in heat exchange tubes 2-1 is continuously cooled by heat exchangewith refrigerant in the evaporator. This cooled fluid is thentransmitted to suitable remotely located heat exchangers through line 72for cooling or dehumidification of the desired areas. The warmed fluidwhich has removed heat from the desired areas is then returned throughline 71 to heat exchange tubes 21 for recooling.

The heat of dilution and condensation of the absorbent solution isremoved from the absorber by passing sea Water or other cooling fluidthrough inlet 61 to tubes 13 and through outlet 6-2 Where the coolingfluid is passed to heat exchange tubes '54 of the condenser.

Capacity control of the absorption refrigeration machine described maybe obtained through control of the concentration of strong solutionreturned from generator 34 to absorber 10. The concentration of theabsorbent solution in turn is controlled by the steam input through line36 by regulation of steam control valve 74. Bulb 73 or other suitabletemperature sensing means is secured to outlet line 72 of evaporator 11and senses the leaving water temperature from the evaporator. When theheat load to be rejected increases, the leaving Water temperature tendsto rise. This rise is sensed by bulb 73 which opens steam valve 74 to aposition such that it passes more steam to the generator. The additionalsteam supplied to the generator concentrates the absorbent to a higherdegree which in turn increases the capacity of the refrigeration systemby increasing the quantity of refrig erant absorbed by the moreconcentrated solution in the absorber.

To prevent solidification and consequent blocking of heat exchanger 31by over-concentrated absorbent being cooled therein below thetemperature at which it solidifies, a suitable bypass valve 42. may heprovided as described in Leonard application Serial No. 2,203, filedJanuary 13, 1960. A purge line 76 and suitable purge 78 are providedadjacent the lower portion of absorber It) to remove noncondensiblesfrom the refrigeration system.

In operation the present invention provides an absorption refrigerationmachine and system which is capable of operating in a plurality ofangular positions such as may be encountered due to pitching and rollingof a seagoing vessel. Such a system is particularly advantageous for airconditioning of a submarine where in addition to the usual pitch androll conditions substantial listing or trim conditions may beexperienced. Further advantages of the refrigeration system describedreside in its relatively noiseless operation and its rapid recovery ratein the event of extremely severe rolls. An additional importantadvantage of a refrigeration machine of the type described lies in thefact that neither the refrigerant nor the absorbent are noxious, toxicor otherwise dangerous to personnel so that leakage which might resultfrom damage to the machine does not present a serious personnel hazard.

Referring particularly to the left hand portion of FIG- URE 2, there isshown a construction of a heat exchanger 69 embodying the instantinvention. Heat exchanger 69 may comprise either a condenser section oran absorber section of the absorption refrigeration machine previouslydescribed. It will be understood that appropriate modifications in thephysical construction of the heat exchanger will be made to especiallyadapt it to its intended purpose. For purposes of illustration heatexchanger 69 has been shown to comprise a condenser of the typeillustrated at 52 of FIGURE 1.

Heat exchanger 69 comprises a shell 70, an inner tube sheet 71 and anouter tube sheet 72. Inner tube sheet "7'1 and outer tube sheet 72 arespaced from each other and secured to shell 70 and to each other by aweld 73. A chamber 74 is formed between the spaced tube sheets 71 and72. It will be understood that other suitable constructions forproviding a chamber between a pair of adjacent tube sheets may beemployed for the purposes of this invention and the illustratedconstruction comprises merely one of a number of possible embodiments ofthis invention.

A passage 75, which is herein shown as being formed in outer tube sheet72, communicates with the interior of chamber 74. A suitable drain valve76 and drain line 77 is secured to tube sheet 72 and serves to withdrawfluids within chamber 74 when the valve 76 is opened. Another passage78, which in the illustrated embodiment, is also formed in outer tubesheet 72, communicates with a valve 79 and a pressure gauge 80. A line$1, which may comprise a sight glass, is shown connected with the otherend of valve 79 and may have appropriate indicia engraved thereon.

A plurality of heat exchange tubes 82 extend through inner tube sheet 71and chamber 74 into outer tube sheet 72. These tubes are appropriatelysecured and sealed in leak-tight engagement with each of the tube sheetsby a rolling operation performed at 83; and 34 respectively. The ends oftubes 32 are open and communicate with water box 85 formed by header 86.Cooling fluid such as sea water is withdrawn from or passed to water box85 through line 87 depending upon the direction of flow of the coolingfluid through heat exchange tubes 82. It will be understood that asimilar construction is desirably formed at the other end of shell 70for a like purpose.

In operation, the absorption refrigeration machine ernbodying a heatexchanger of the type described is assembled and valves 76, 79 areopened to drain any condensed moisture or other fluids which may haveaccumulated in chamber 74. Valve 76 is then closed and a suitable,compatible, substantially incompressible fluid such as octyl alcohol, inits liquid state, is poured into chamber 74 through line 81 at whichtime valve 7% is open. Chamber 74 is filled with the desired liquid to alevel at least above that of the highest tube 82 and preferably to alevel somewhere in line 31, which is located above pressure gauge 86 andvalve 79. Valve 79 may then be closed after assuring that no trappedcompressible fluids remain in the system such as in pressure gauge 80.Thereafter, variations of pressure within chamber 74 will be transmittedthrough the incompressible fluid and passage 78 to pressure gauge Stwhere they will become observable.

If a leak is experienced between one of the tubes 82 and outer tubesheet 72, the pressure of cooling fluid, such as sea water, will betransmitted to the incompressible fluid in chamber 74 and manifest itsexistence by an abnormal rise in pressure on gauge 80. If on the otherhand, a leak develops between inner tube sheet 71 and one of the heatexchange tubes 82, the incompressible fluid in chamber 74 will find itsway through the leak into the interior of heat exchanger 69 due to therelatively low pressure maintained therein. Consequently, a leak of thistype will manfiest itself by an abnormally low pressure reading on gauge89. If the fluid in chamber 74 3,1 eases is selected to be compatiblewith the contents of the absorption refrigeration machine of which heatexchanger 69 is a part, no adverse effect need result from leakage ofthe fluid into the heat exchanger.

An additive which is commonly present in the absorption refrigerationmachine such as octyl alcohol (2-ethyln-hexanol) makes a desirableliquid with which to fill chamber 74. Under these conditions leakage ofoctyl alcohol into the absorption refrigeration machine does not causecorrosion or have a deleterious effect on the performance of therefrigeration system, while at the same time the liquid octyl alcoholtends to form a liquid seal against the entrance of vapors or otherforeign materials which might find their way into the absorptionrefrigeration machine.

While pressure gauge 80 has been shown by way of example as a convenientmeans for observing abnormal changes in pressure in chamber 74 which areindicative of leaks between a tube and its associated tube sheet, the

pressure gauge may be omitted if desired. Instead, valve A 79 may remainopen and leaks detected by simply observing abnormal changes in thepressure or level of octyl alcohol in the chamber by means of sightglass 81. Under these circumstances, it is preferable to employ a ventedplug 88 in the top of sight glass 81 to substantially prevent theejection of large quantities of octyl alcohol from the top of sightglass 81 in the event of a large leak between outer tube sheet 72 andtubes 82.

Referring now to the right hand portion of FIGURE 2, there is shown afurther modified form of indicator mechanism 90. Indicator mechanism 90comprises a bellows 92 disposed within a can 91. Bellows 92 is sealinglyattached at one end adjacent the bottom or side of can 91 which isdesirably cylindrical in cross-section. An indicator bar 93 havingappropriate indicia thereon is secured adjacent the upper portion ofbellows 92 and projects through an aperture in can 91 to permit visualobservation of the position of the bellows. The underside of bellows 92is in communication with inner chamber 74 through passage 73 in outertube sheet 72. Consequently, changes in pressure in inner chamber 74 aremanifested by upward or downward movement of bellows 92 and indicatorbar 3 from a predetermined normal range of positions.

It will be observed that by the practice of the invention, a simple andreliable indicator means is provided by which relatively small leaksbetween a tube sheet and its associated heat exchange tubes may beindirectly detected in spite of the relative difficulty of directobservation. Such an arrangement is particularly desirable for use inseagoing vessels such as submarines wherein the tubes and tube sheetsmay be subjected to severe mechanical stresses and strains or whereinthey are exposed to high submergence pressures which may cause smallleaks to develop into larger ones which seriously impair or renderinoperative an absorption refrigeration system.

While preferred embodiments of this invention have been shown anddescribed in detail for purposes of illustration, it will be understoodthat the invention may be otherwise embodied within the scope of thefollowing claims.

I claim:

1. In an absorption refrigeration machine comprising an absorber, agenerator, a condenser and an evaporator operatively connected in arefrigeration circuit, said condenser and said absorber each comprisingheat exchangers, the improvement comprising at least one of said heatexchangers having a pair of tube sheets at one end thereof, each of saidtube sheets being spaced from each other and forming a chambertherebetween, each of a plurality of heat exchange tubes being sealinglyengaged with both of said pair of tube sheets, a substantiallyincompressible fluid filling said chamber to a level above said tubes,and m a s re ponsive to both increased and decreased changes in pressureexerted on said fluid to indicate leakage at said chamber.

2. An absorption refrigeration machine as defined in claim 1 wherein theabsorption refrigeration machine is of the type utilizing a hydroscopicabsorbent solution comprising lithium bromide and wherein saidsubstantially incompressible fluid comprises octyl alcohol.

3. An absorption refrigeration machine as defined in claim 1 whereinsaid means responsive to pressure comprises an indicator responsive tothe level of fluid in said chamber to detect leakage to and from saidchamber due to pressure being exerted on said liquid.

4. An absorption refrigeration machine as defined in claim 1 whereinsaid means responsive to pressure comprises a pressure gauge.

5. An absorption refrigeration system comprising an absorber, anevaporator, a generator, and a condenser, said absorber and saidcondenser comprising heat exchangers, the improvement comprising one ofsaid heat exchangers having an inner tube sheet and an outer tube sheet,said tube sheets both being disposed in spaced relationship at one endof said heat exchanger, a plurality of heat exchange tubes in said heatexchanger having open portions adapted to pass a heat exchange fluid,said plurality of heat exchange tubes passing through said inner tubesheet and being in sealed engagement therewith, said plurality of tubesalso passing into said outer tube sheet and being in sealed engagementtherewith, a fluid header disposed about the open portions of said heatexchange tubes, means including said spaced inner and outer tube sheetsdefining a substantially closed chamber between said tube sheets, inletmeans communicating with said chamber to admit a substantiallyincompressible fluid into said chamber, and means to indicate thepressure exerted on the fluid in said chamber to indicate leakage ofsaid chamber at the joints between said heat exchange tubes and saidtube sheets.

6. An absorption refrigeration system as defined in claim 5 wherein saidheat exchanger comprises an absorber vessel in an absorptionrefrigeration system adapted for use aboard a submarine vessel andwherein said fluid header is adapted to be exposed to submergencepressures.

7. An absorption refrigeration system as defined in claim 5 wherein saidheat exchanger comprises a condenser vessel in an absorptionrefrigeration system adapted for use aboard a submarine vessel andwherein said fluid header is adapted to be exposed to submergencepressures.

8. An air conditioning system for use in a submarine vessel comprising arefrigeration machine, said refrigeration machine comprising a heatexchanger of the tubeand-sheet type, said heat exchanger comprising aninner tube sheet and an outer tube sheet, said tube sheets both beingdisposed in spaced relationship at one end of said heat exchanger, aplurality of heat exchange tubes in said heat exchanger having openportions adapted to pass a heat exchange fluid, said plurality of heatexchange tubes passing through said inner tube sheet and being in sealedengagement therewith, said plurality of tubes also passing into saidouter tube sheet and being in sealed engagement therewith, a fluidheader disposed about the open portions of said heat exchange tubes,said fluid header being adapted to pass sea water at high pressures whensaid vessel is submerged, means including said spaced inner and outertube sheets defining a substantially closed chamber between said tubesheets, inlet means communicating with said chamber to admit asubstantially incompressible fluid into said chamber, and meansresponsive to deviation from normal pressure exerted on the fluid insaid chamber to indicate leakage of said chamber at the joints betweensaid heat exchange tubes and said tube shee.

9. A heat exchanger comprising an inner tube sheet and an outer tubesheet, said tube sheets both being disposed in spaced relationship atone end of said heat exchanger, a plurality of heat exchange tubes insaid heat exchanger having open portions adapted to pass a heat exchangefluid, said plurality of heat exchange tubes passing through said innertube sheet and being in sealed engagement therewith, said plurality oftubes also passing into said outer tube sheet and being in sealedengagement therewith, a fluid header disposed about the open portions ofsaid heat exchange tubes, means including said spaced inner and outertube sheets defining a substantially closed chamber between said tubesheets, inlet means communicating with said chamber to admit asubstantially incompressible fluid into said chamber and means toindicate deviation from normal pressure exerted on the incompressiblefluid in said chamber to indicate leakage of said chamber at the jointsbetween said heat exchange tubes and said tube sheets.

References Cited in the file of this patent UNITED STATES PATENTS1,948,550 Voorheis Feb. 27, 1934 2,658,728 Evans Nov. 10, 1953 2,743,089Gardner et a1 Apr. 24, 1956 2,893,701 Bell July 7, 1959 FOREIGN PATENTS1,128,665 France Jan. 9, 1957

1. IN AN ABSORPTION REFRIGERATION MACHINE COMPRISING AN ABSORBER, AGENERATOR, A CONDENSER AND AN EVAPORATOR OPERATIVELY CONNECTED IN AREFRIGERATION CIRCUIT, SAID CONDENSER AND SAID ABSORBER EACH COMPRISINGHEAT EXCHANGERS, THE IMPROVEMENT COMPRISING AT LEAST ONE OF SAID HEATEXCHANGES HAVING A PAIR OF TUBE SHEETS AT ONE END THEREOF, EACH OF SAIDTUBE SHEETS BEING SPACED FROM EACH OTHER AND FORMING A CHAMBERTHEREBETWEEN, EACH OF A PLURALITY OF HEAT EXCHANGE TUBES BEING SEALINGLYENGAGED WITH BOTH OF SAID PAIR OF TUBE SHEETS, A SUBSTANTIALLYINCOMPRESSIBLE FLUID FILLING SAID CHAMBER TO A LEVEL ABOVE SAID TUBES,AND MEANS RESPONSIVE TO BOTH INCREASED AND DECREASED CHANGES IN PRESSUREEXERTED ON SAID FLUID TO INDICATE LEAKAGE AT SAID CHAMBER.